In data centers and other industrial environments, a power source is typically provided to information technology (“IT”) equipment with a three-phase busway that carries current. Each phase can be provided separately to different types of IT equipment. In some instances, the three-phase busway provides power to a rack that holds electrical equipment such as servers. The IT equipment located in the rack receives power from the busway via a PDU mounted to the rack frame. The PDU includes a connection to the three-phase busway, and a plurality of components to provide, regulate, and monitor the current being distributed to the IT equipment in the rack.
PDUs have many circuit protection options, and may include, without limitation, a single circuit breaker, multiple circuit breakers, a single fuse, multiple fuses, one or more residual-current devices, one or more reclosers, one or more polyswitches, and any combination of these and other protection devices. Such devices may broadly be referred to as circuit protection devices. A PDU may be configured to accept a three-phase wye voltage input, a three-phase delta voltage input, or a single-phase voltage input. Due to the many variations of circuit protection devices in PDUs, integrated measurements have not been able to be used. Instead, current transformers have been used on wires to provide flexibility of placement.
It is desirable to measure the output voltage of circuit protection devices to detect if a circuit protection device has tripped, blown, or otherwise faulted. To do so, however, requires another set of control wires connected to the output of each protection device. The resulting number of wires can be difficult to manage and may increase the size of the PDU.